A variety of radiation imaging techniques and devices are known in the art. One example of radiation imaging devices includes X-ray machines, which have been used for many years to determine the internal structure of humans, animals, and other living and nonliving things. One problem with prior art X-ray machines is that the amount of X-radiation required for a suitable image can have deleterious effects on the subject. Common X-ray machines also are limited because only a single image can be produced and then the X-ray film or plate must be replaced before another image can be made. This system is impractical or impossible to use in producing real-time images. Real-time imaging refers to imaging wherein the image can be displayed simultaneously or nearly simultaneously with the occurrence of the event and preferably in a continuous manner.
Real-time radiation imaging has many potential applications which are not possible at this time because of the inability to very rapidly retrieve image information which has been stored in a luminescent phosphor screen. The idea of using luminescent phosphor screens in radiation imaging is not new and is shown in U. S. Pat. No. 3,975,637 to Ikedo et al. The Ikedo invention is directed to producing an X-ray image on an image storing panel which has a layer of thermoluminescent material or phosphor. The thermoluminescent phosphor stores thermoluminescent energy in an amount dependent upon the amount of X-radiation which strikes the panel. The stored thermoluminescent energy is then released using a laser beam which heats the phosphor at individual points across the screen. The heated phosphor releases the stored thermoluminescent energy creating a visual light emission which is measured with an optical detector and the measurement information is stored so that a composite image can be formed from a large number of points on the screen. The composite image can be used to produce a visual image on a cathode ray tube or similar display. The thermoluminescent stimulation of Ikedo is much too slow for real-time imaging since each scanning of the panel requires 5 seconds. The basic thermoluminescent stimulation process requires heating of each point so it is impossible to reduce the scanning time so that 25-30 images can be produced each second, as required to produce a flicker free real-time image.
U.S. Pat. No. 4,258,264 to Kotera et al discloses a method and apparatus for reading out a radiation image recorded in a stimulable phosphor. The Kotera invention also shows laser stimulation of a phosphor screen for the purpose of producing a radiation image. Kotera, like Ikedo, teaches a phosphor stimulation technique which is much too slow for real-time imaging. Kotera indicates phosphor response times of greater than 100 microseconds and in one example explains that total scanning time for a phosphor plate as being in the range of 5 minutes. Such stimulation and response times are not able to produce real-time images and these patents do not contemplate such an important advancement in the art of luminescent radiation imagery.
The current invention solves the problem of real-time radiation imaging by using novel features which allow for very rapid stimulation of a phosphor panel or screen. The invention also allows the radiation exposure to be kept at very low values, thereby allowing continuous images to be made without deleterious effects upon the subject. Continuous real-time imaging allows a doctor or other examiner to view a body as it is moved into different positions, thereby providing much more effective information for diagnosis or analysis. Other objects and advantages of the invention will be apparent from the specification and claims.